The rail firm which cancelled most of its services last Sunday because of staff shortages is facing the threat of industrial action in a row over pay, it was revealed today.

London Midland, which operates more than 1,200 services a day to 149 stations, was criticised after revealing its drivers usually worked on a voluntary basis on Sundays and not enough staff volunteered to work last weekend.

The company last night offered an extension to enhanced overtime payments in a bid to avoid a repeat of disruption to services this weekend.

Leaders of the Rail Maritime and Transport union were meeting today to consider balloting its members at the company for industrial action in a long-running row over harmonisation of pay and conditions.

The row broke out earlier this year but has flared again, threatening a fresh headache for the company.

London Midland has announced that enhanced payments for Sunday working will be for an extended period while it seeks a long-term solution to weekend arrangements.

A company spokesman said: "To ensure that London Midland passengers are not inconvenienced by further cancellations and disruptions with Sunday services, managers have advised Aslef and the RMT we will continue to offer enhanced overtime payments for drivers and conductors working Sunday shifts.

"This is again for a time-limited period and we will be continuing to seek a longer term solution."

The RMT said it will be known by midnight tonight if enough people have volunteered to work this weekend.